Working Scientifically

Question 1

What are the 3 variables in an investigation?

Answer 1

1. independent variable
2. control variable
3. dependent variable

Question 2

What is an independent variable?

Answer 2

the variable that is changed

Question 3

What is a dependent variable?

Answer 3

the variable that is measured

Question 4

What is a control variable?

Answer 4

variables that are kept the same throughout the investigation

Question 5

Why are control variables important?

Answer 5

Control variables must be keep the same because otherwise we can’t be certain that any changes in the dependent variable are caused only by changes in the independent variable.

Question 6

In exam questions that ask you to describe a required practical, what should you remember to identify?

Answer 6

Make sure you identify the independent and dependent variables and describe what will be done to keep the control variables the same.

Question 7

What are the two types of error?

Answer 7

1. random
2. systematic

Question 8

What is a random error?

Answer 8

An error that causes random variation in the results.

Question 9

What is a systematic error?

Answer 9

An error that causes the results to differ from the true value by a consistent amount for every reading.

Question 10

Give an example of a random error.

Answer 10

• reading a thermometer incorrectly (not at eye level)
• starting a stopping a timer - different reaction times mean that the timer will be pressed at a slightly different time to the true value

Question 11

How could parallax error (getting an incorrect value when reading a thermometer due to not being at eye level with it) be prevented?

Answer 11

use a digital thermometer

Question 12

Give an example of a systematic error.

Answer 12

faulty equipment

Question 13

What is a zero error and what type of error is it.

Answer 13

• where measuring equipment should read zero but doesn’t
• type of systematic error

Question 14

How can random errors be avoided?

Answer 14

• can never be completely avoided
• their effect can be reduced by taking more measurement and calculating a mean

Question 15

How can systematic errors be avoided?

Answer 15

If a systematic error is suspected then the experiment should be done again with a different technique or equipment.
Alternatively, if a zero error has occurred then the value measured at zero can be subtracted.

Question 16

What is precision?

Answer 16

The range of values we get when we do repeats. A more precise range is one that’s more tightly clustered around the mean

Question 17

What does the level of precision depend upon?

Answer 17

The extent of random errors. Greater precision means there were fewer random errors.

Question 18

What does the precision of a measurement not show?

Answer 18

Whether a zero error occurred.
Precision only shows the extent of random eros and not whether or a not a measurement is accurate.

Question 19

What is uncertainty?

Answer 19

The fact that we can never be certain if the accurate value of a measurement due to there always being some level of random error.

Question 20

How is uncertainty calculated?

Answer 20

Range of values
Uncertainty = ————————
2

Question 21

What does repeatable mean?

Answer 21

If the same person does an experiment again using the same methods and equipment they will get a similar result.

Question 22

What does reproducible mean?

Answer 22

If someone else does the experiment and/or they use a different method or equipment then the results will be similar.

Question 23

What does it mean if data is both repeatable and reproducible?

Answer 23

it is reliable

Question 24

What are valid results?

Answer 24

Results that are:
- repeatable
- reproducible
- that answer the original question
- that come from experiments which were fair tests